US9029308B1

US9029308B1 - Low foam media cleaning detergent

Info

Publication number: US9029308B1
Application number: US13/433,037
Authority: US
Inventors: Soh Kian Koo; Kok Kin Yap; EE Boon Quah
Original assignee: WD Media LLC
Current assignee: Western Digital Technologies Inc
Priority date: 2012-03-28
Filing date: 2012-03-28
Publication date: 2015-05-12

Abstract

A chemical composition for cleaning a medium is provided. For some embodiments, the chemical composition comprises a nonionic surfactant, an inorganic salt, a glycol compound, a chelating agent, and deionized water. For example, the chemical composition may comprise between about 1% and 5% of nonionic surfactant, between about 2% and 6% by weight of an inorganic salt, between about 5% and 10% by weight of a glycol compound, between about 5% and 10% by weight of a chelating agent, and deionized water.

Description

TECHNICAL FIELD

Invention(s) described herein relate to cleaning processes and detergents used in cleaning media and, more particularly, processes and detergents used during the manufacturing of hard drive media.

BACKGROUND

Disk media used in hard drives may include a substrate that is plated with a material such as nickel or cobalt. Subsequent to plating, a disk medium is usually polished using chemical mechanical polishing process, which exposes the surface of the disk medium to a number of different contaminants. The containments may be the result of the polish slurry, polish residue, media manufacturing equipment, or the media manufacturing environment. For instance, polishing slurry has a tendency to bond to the surface of disk media making contamination particles from the slurry difficult to remove. If contamination particles are not removed from the surface of a plated and polished disk medium, the operation and performance of a hard drive incorporating the disk medium may be negatively impacted.

Accordingly, disk manufacturers regularly utilize detergents and cleaning processes to remove contaminants from the surface of disk media before proceeding with subsequent manufacturing processes (e.g., sputter process). Unfortunately, use of certain cleaning processes and detergents are known to leave behind blisters and water stains on the surface of disk media. These blisters and water stains can result in major glide loss over the surface of a disk medium.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not limitation, in the figures of the accompanying drawings. With respect to the figures:

FIG. 1 illustrates the removal of organic residue from a surface of a disk medium in accordance with some embodiments of the present invention;

FIG. 2 illustrates the removal of inorganic particles from, a media substrate surface in accordance with some embodiments of the present invention;

FIG. 3 illustrates the removal of a metal ion from a media substrate surface in accordance with some embodiments of the present invention;

FIG. 4 provides images of a cleaning tank after use of an exemplary chemical composition in accordance with some embodiments of the present invention; and

FIG. 5 is a flowchart illustrating an exemplary method for manufacturing and cleaning a disk medium in accordance with some embodiments of the present invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth to provide a thorough understanding of various embodiments of the present invention. It will be apparent however, to one skilled in the art that these specific details need not be employed to practice various embodiments of the present invention. In some instances, well known components or methods have not been described in detail to avoid unnecessarily obscuring various embodiments of the present invention.

Various embodiments of the present invention provide for a chemical composition, or use of the chemical composition, for cleaning a medium, such as disk media used in hard drives. In certain instances, the chemical composition may be utilized as a post-polish detergent in cleaning processes performed on disk media during their manufacturing.

For example, a post-polishing cleaning process using the chemical composition may take place after a disk medium has been plated and polished (where the polishing process provides the disk medium with an even, uniform surface). The plated disk media to be cleansed with the chemical composition may be polished using chemical mechanical polishing, which can introduce a number of contaminants to the disk medium surface (e.g., from polishing slurry, polish residue, or exposure to the manufacturing environment and machinery). During a cleaning process, the chemical composition may remove, for example, polishing slurry residues that have dried out on media substrate surfaces (e.g., containing aluminum oxide, colloidal silica or organic coolant). In various embodiments, the chemical composition employs surfactants to remove contaminants from the disk medium surface and enhance an automatic cleaning machines performance (e.g., cleaning machines by Speedfam Clean System Co., Ltd. used in disk media cleaning).

For some embodiments, the chemical composition comprises a nonionic surfactant, an inorganic salt, a glycol compound, a chelating agent, and deionized water. In particular instances, the chemical composition may comprise between about 1% and 5% of nonionic surfactant, between about 2% and 6% by weight of an inorganic salt, between about 5% and 10% by weight of a glycol compound, between about 5% and 10% by weight of a chelating agent, and deionized water. Depending on the embodiment, the nonionic surfactant may comprise polyoxyethylene arylether and polyoxyethylene phenyl, the inorganic salt may comprise potassium hydroxide, and the glycol compound may comprise dipropylene glycol methyl ether (HEDP). The medium may be a metal comprising Ni or W.

According to various embodiments, the chemical composition may assist in reducing circular blister and water stains caused that may be left after a cleaning process. This reduction may increase the quality of disk media produced during a disk media manufacturing process. The chemical composition may have a low foam property. With a low foam property for the chemical composition may determine the degree of bubbles trapped in a cleaning tank after a disk medium cleaning process. Generally, bubbles limit the flow of particles in and out of a cleaning tank (e.g., moving from the overflow out, to the inner tank, and to the drain path or from the overflow tank return, to the circulation and filtration loop). Bubbles can also remain on a (disk medium) carrier, and carry forward as a disk medium is transferred to a subsequent cleaning operation (eventually resulting in circular type of blister defect).

Furthermore, the chemical composition may be free from an amine compound, may have a low ionic/corrosion level, and may have thermal stability. For example, in dilute conditions, the chemical composition may have a cloud point above 90° C. temperature that is cleaner than other chemical compositions used as detergents.

In addition, in comparison to other chemical compositions used in cleaning disk media, the chemical composition in accordance with some embodiments may be safer for human health, may be safer for the environment, may exhibit better cleaning performance (e.g., with respect to colloidal silica slurry removal), may exhibit better chemical rinse ability. In another example, any chemical residue left by the chemical composition may be easily rinsed away from the disk medium media by a rinsing process using deionized (DI) water.

As described herein, for some embodiments, the chemical composition may be utilized in a method for cleaning a disk medium, comprising ultrasonically cleaning the medium using the chemical composition, and mechanically scrubbing the medium using the chemical composition. The method for cleaning the disk medium may further comprise rinsing the medium using deionized water. Depending on the embodiment, the method may be performed before a sputtering process is performed on the disk medium.

FIG. 1 illustrates the removal of organic residue 104 from a surface of a disk medium 102 in accordance with some embodiments of the present invention. When surface of the disk medium 102 is soaked in the chemical composition of some embodiments, the organic residue 104 can be loosened easily. The hydrophobic tail of the nonionic surfactant may attach the organic residue 104 and, at the same time, the opposite force of the hydrophilic head of the surfactant will pull organic residue 104 away from the surface of the disk medium 102. Once residue 104 has been removed, micelles in the chemical composition of some embodiments will keep organic residue 104 emulsified, suspended and dispersed so it does not redeposit back onto the surface of the disk medium 102 again.

FIG. 2 illustrates the removal of

inorganic particles

204 a, 204 b, and 204 c from a surface of the disk medium 202 in accordance with some embodiments of the present invention. In order to remove inorganic particles, such as the alumina and silica generally used in and left behind by a polishing slurry, the chemical composition of some embodiments changes the surface electrical charges so that

inorganic particles

204 a, 204 b, and 204 c are repelled both from the surface of the disk medium 202 and from each other.

FIG. 3 illustrates the removal of a metal ion 304 from a surface of a disk medium 302 in accordance with some embodiments of the present invention. In order to remove metal ions, the chemical composition of some embodiments may include a chelating agent. In one example, the chelating agent may comprise hydroxyethylene disphosphonic acid (HEDP) to assist in the removal of many different metal ions, such as Ca²⁺, Cu²⁺, Fe²⁺, Zn²⁺, Fe³⁺, and Ni²⁺, with which HEDP can form a six-member ring chelate. Typically, HEDP exhibits good chemical stability under high pH values, and is resistant to being hydrolyzed, due to HEDP's structure including all C—P bonds. In some embodiments, the chelating agent may be any that utilizes all C—P bonds.

To further assist in the removal of inorganic particles, the chemical composition of some embodiments may comprise an inorganic salt operative in controlling the pH. Examples of inorganic salt in the chemical composition may include, without limitation, potassium hydroxide. The potassium hydroxide may establish a pH of between about 12.0 and 12.5, in order to create an etching effect on the disk medium surface to be cleaned. In addition to creating the etching effect, maintaining a pH between 12.0 and 12.5 by using potassium hydroxide may allow the chemical composition to maintain a repulsive force between the disk medium surface and common inorganic contaminants, such as those listed below in Table 1 with their corresponding iso-electrical point (IEP) value.

TABLE 1

Inorganic particle	Iso-Electrical Point (IEP) value

SiO₂(silica)	1.7-3.5
Fe₃O₄(magnetite)	6.5-6.8
CeO₂(ceria)	6.7-8.6
Al₂O₃(gamma alumina)	7-8
Fe₂O₃(hematite)	8.4-8.5
Al₂O₃(alpha alumina, corundum)	8-9
NiO	10-11

In view of the Table 1, to create a repulsive force (i.e., a negative charge) for the listed media contaminants, the pH of the chemical composition for some embodiments may be set above 11. Because excessively high pH values may cause the chemical composition instability and chemical compatibility issues, in some embodiments, the chemical composition may comprise an inorganic salt to have a pH value of about 12.1.

FIG. 4 provides

images

400 a and 400 b of a cleaning tank after use of an exemplary chemical composition in accordance with some embodiments of the present invention. In addition to exhibiting great cleaning performance, the chemical composition of some embodiments enjoy improved rinsability.

To increase the chemical thermal stability of the chemical composition of some embodiments, nonionic surfactants with high ethoxylation (EO) levels in the chemical composition may increase the cloud point of the chemical composition to more than 90° C. when in a dilute condition. For some embodiments, the high cloud point in the chemical composition may be desirable as the tank water temperature for cleaning application can go as high as 60° C. The nonionic surfactant of the chemical composition may have a high EO level, such as, for example, between about 5 and about 20, to assist in preventing cloud formation in these conditions.

FIG. 5 is a flowchart illustrating an exemplary method 500 for manufacturing and cleaning a disk medium in accordance with some embodiments of the present invention. The method 500 may begin at operation 502, with the plating of a disk medium utilized in a hard drive. After polishing the plated disk medium at operation 504, the plated disk medium may be ultrasonically cleaned using a chemical composition as described herein at operation 506. The plated disk medium may be subsequently rinsed by deionized (DI) water at operation 508 and then mechanically scrubbed using the chemical composition at operation 510.

In the foregoing specification, embodiments of the invention have been described with reference to specific exemplary features thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and figures are, accordingly, to be regarded in an illustrative rather than a restrictive sense. As such, though various embodiments disclosed herein are described with respect to a disk medium for hard drives, those skilled in the art will appreciate that various embodiments may be utilized with other types of media, which may or may not relate to hard drives.

Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as meaning “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; the terms “a” or “an” should be read as meaning “at least one,” “one or more” or the like; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future.

A group of items linked with the conjunction “and” should not be read as requiring that each and every one of those items be present in the grouping, but rather should be read as “and/or” unless expressly stated otherwise. Similarly, a group of items linked with the conjunction “or” should not be read as requiring mutual exclusivity among that group, but rather should also be read as “and/or” unless expressly stated otherwise. Furthermore, although items, elements or components of the invention may be described or claimed in the singular, the plural is contemplated to be within the scope thereof unless limitation to the singular is explicitly stated.

Claims

What is claimed is:

1. A chemical composition for cleaning a medium, the chemical composition comprising:

a nonionic surfactant having an ethoxylation level between about 5 to 20, wherein the nonionic surfactant comprises polyoxyethylene arylether and polyoxyethylene phenyl ether;

a medium etching component comprising an inorganic salt, the inorganic salt creating a pH of the chemical composition that is between about 12.0 to 12.5 at a temperature up to about 60 degrees Celsius;

a glycol compound;

a chelating agent; and

deionized water.

2. The chemical composition of claim 1, wherein the polyoxyethylene arylether is about 1 to 5 wt. % of the chemical composition.

3. The chemical composition of claim 1, wherein the polyoxyethylene phenyl ether is 1 to 5 wt. % of the chemical composition.

4. The chemical composition of claim 1, wherein the inorganic salt comprises potassium hydroxide.

5. The chemical composition of claim 4, wherein the potassium hydroxide is about 2 to 6 wt. % of the chemical composition.

6. The chemical composition of claim 1, wherein the glycol compound comprises dipropylene glycol methyl ether.

7. The chemical composition of claim 6, wherein the dipropylene glycol methyl ether is about 5 to 10 wt. % of the chemical composition.

8. The chemical composition of claim 1, wherein the chelating agent comprises hydroxyethylene disphosphonic acid (HEDP).

9. The chemical composition of claim 8, wherein the hydroxyethylene disphosphonic acid (HEDP) is about 5 to 10 wt. % of the chemical composition.

10. The chemical composition of claim 1, wherein the medium is a magnetic medium.